Add getHal and getHals to VendorManifest.

Part of the effort to hide implementation details in libvintf.

Bug: 34620633

Test: libvintf_test
Change-Id: I673fa29be833f023ffe29ece0b3295cec2203e19
diff --git a/parse_xml.cpp b/parse_xml.cpp
index 3070771..5f1e2e4 100644
--- a/parse_xml.cpp
+++ b/parse_xml.cpp
@@ -406,8 +406,8 @@
     std::string elementName() const override { return "manifest"; }
     void mutateNode(const VendorManifest &m, NodeType *root, DocType *d) const override {
         appendAttr(root, "version", VendorManifest::kVersion);
-        for (const auto &pair : m.hals) {
-            appendChild(root, manifestHalConverter(pair.second, d));
+        for (const auto &hal : m.getHals()) {
+            appendChild(root, manifestHalConverter(hal, d));
         }
     }
     bool buildObject(VendorManifest *object, NodeType *root) const override {